Water tube boiler



www@ l Feb M, w36. J. o. NYGAARD WATER TUBE OILER Filed June 11, 1932 v4sheets-snaai 1 q l? M Feb. M, i936.

J. o, NYGAARD WATER TUBE BOILER Filed June 11, 1952 .www m MW 4Sheets-Sheet 2 Feb. 11, 1936. J. o. NYGAARD WATER TUBE BOILER 4Sheets-Sheet 3 Filed June 1l, 1932 gaard,

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Feb M, 1936., J, o. NYGAARD WATER TUBE BOILER 4 Sheds-Sheet 4 Filed Junell, 1932 Patented Feb. 11, 1936 Ni'i'D STATES PATENT OFFICE ApplicationJune 11, 1932, Serial No. 616,717 In Norway June 12, 1931 14 Claims.

The present invention relates to an improved water tube boiler. Thisimprovement results in a more compact and advantageous construction thanhitherto and is based upon different important and new features formingparts of the total invention.

A principal and basic feature resides in this that a combustion chamberwhich is arranged in well-known manner as a centrally located core, issurrounded by at least two preferably circular layers of boiler tubesand one or more smoke gas channels, the tubes of at least one tube layerbeing at one or both ends mounted slidably in their headers, and theseheaders are supported by an exterior pulling member, preferably thesurrounding boiler shell, so that the latter receives as tensilestresses the forces produced by the steam pressure and tending to pressapart from one another the headers at both ends of the boiler tubes.

Another important feature resides in the combustion chamber constitutinga central heat radiating Wall surrounded by at least two layers ofboiler tubes and smoke gas channels receiving the principal proportionof the radiating heat and protecting to the greatest extent the exteriorboiler shell against heat. The tubes of the inner layer may be providedwith wings welded thereto along the portion of their periphery facingapart from the radiating wall. The said wings should be so located as toreceive not only heat from sweeping smoke gases but also the radiatingheat passing from said walls outwards between the tubes and thereby toconduct such heat to the eX- terior sides of the tubes.

The slidably mounted vaporizing tubes are provided vvith means to causesaid tubes to vaporize the water received in one end from the collectingwater header and to superheat in the other tube end the steam producedin the middle tube portion and to conduct such superheated steam to theheader at said other tube end.

Each boiler tube layer may project into annular distributing andcollecting headers divided into segments supported by the surroundingboller shell, the interior parts and members of the boiler being soshaped in relation to one another that they intersupport each other andare assembled in their relative position by4 the boiler shellsurrounding and binding together the whole structure in such a mannerthat the several interior parts and members, upon the shell having beenopened, may be picked out in a definite succession. Y

The most heat is supplied to the wall portion around the llame. When thegases in the smoke gas channel outside the said wall approach this wallportion, they have a temperature far below that of said portion, becausethey have given oi an essential part of their heat to the boiler tubes(Vaporizer and/or superheater) In order to obtain an eiiicientheat-delivery from the smoke gases also along the said wall portion, itis advantageous to arrange a heat-absorbing member, for instance anintermediate superheater between the wall and the smoke gases, so thatthe latter enter here in contact with the wall.

Such an intermediate superheater may consist of one or two layers oftubes, one of which may suitably be so-called wing-tubes, in order toform thereby a somewhat tight wall against the heat rays from the innerwall.

Other features of the invention will be eX- plained hereinafter inconnection with the drawings.

Fig. l shows a diagrammatical longitudinal section of a boilerconstructed in accordance with the invention. Fig. 2 shows a part of across section of same on the line II-II of Fig. 1 and shows thediiierent layers of boiler tubes, insulating material, smoke gaschannels and combustion channel.

Fig. 3 shows in a larger scale a longitudinal section of the boilerportion adjacent the lowermost collecting and distributing headers andin a somewhat modied form.

Fig. 4 shows similarly a part of a longitudinal section of the boilerportion adjacent the uppermost headers.

Figs. 5 and 5a show in a larger scale longitudinal sections of a boilertube with inserted steam guiding members.

Fig. 6 shows a cross section through a plurality of the tubes shown inFig. 5 and adjacent parts.

Figs. and 8 show certain details.

In Figs. 1 and 2 the air inlet is shown at I. 2 is the combustionchamber, 3 the inner smoke gas 45 channel, 4 the exterior smoke gaschannel which is divided up into smoke gas tubes arranged inside theboiler tubes.

5 is the gas outlet, 6 the water supply to the preheater, l' the conduitpassing the preheated 50 water to the pump, 8 the conduit passing fromthe pump to the steam vaporization member, 9 outlet for steam, I0 thesupply of combustible,

II inlet to the intermediate superheater and I2 outlet from same. I3 isthe Wall surrounding the 55 combustion chamber and is supported by theglow-vault I4 above said chamber. I5 is the distributing header, It thetubes and I'I the collecting header for the water preheating member. I8the distributing header, I9 the tubes and 2&3 the collecting header forthe vaporizing and superheating members, 2l and 22 are the insulatinglayers outside and inside the water preheating members respectively. 23is the boiler shell which is strongly anchored to the foot 24 and to thetop piece 25, the latter 24 and 25 forming supporting members for theheaders and serving also to receive the compressing strains from themedium in the longitudinal direction of the tubes and to transfer suchstrains to the boiler shell. 2S is the distributing header, 21a. theexterior, 2lb the interior tubes and 2B the collecting header of theintermediate superheater.

As indicated in Fig. l one or more of the tubes I@ (without interiortubes 4) are used as inlet 6 for feed Water. Into these tubes I5 thecold feed Water is pumped and passes up to the distributing header I5and from the latter again downwards through all the normal tubes I6(with interior smoke tubes 4) to the lower water collecting header I8,then from same through a lateral channel 'I out into an exterior conduit5I containing an energie pressure pump 50. This pump now forces thisfeed water well preheated through a lateral inlet 8 into thedistributing header I8. Fig. 7 indicates constructional forms of themembers 5, 'I and 8.

In the constructional form shown in Fig. 3 the lowermost collecting anddistributing headers are supported by ribs 29 of the intermediatesuperheater header 2G made as a closed ring and transferring thecompressive strains from the medium (water or steam) to the shell 23,the header 26 resting in the ring 30 Which is safely anchored to theshell for instance by rivets or by welding. Fig. 3 also shows, how theinlet II to the header 26 and outlet I2 from header 28 may be suitablyarranged. The ring SI, preferably divided into two parts, is a looseextension of the collecting header I'I and has principally for itspurpose to conduct the smoke gases from gas channel 3 (Figure 1) througha curved path into the smoke gas tubes 4.

32 is a ring provided with feet 33, whereby the walls etc. forming thecombustion chamber are supported on the header 2t and thereby on theboiler shell 23. 2!! is the foot piece, upon which the boiler rests. Sliand 49 (Figs. 3 and 4) are some brackets riveted or weided to the boilershell and retaining the headers I'I, I3, I5, and 2B in position, whenthe boiler is out of operation. 35 is a shielding wall to prevent thesmoke gases from reaching the wall I3 and the comparatively hot tubes2lb. il! are soft packings (for instance an asbestos cord) to protectagainst the smoke gases under over-pressure. l2 is a calked tighteningring of copper or the like, 63 a protecting ring of a suitable materialand 44 a spring-ring retaining it in position. 45 is a thin metal sleevewhich may be attached to the tube end or be made by thinning out sameand has engagement with a slide-bearing in the header I3. This sleevewhich may also be attached to the slide-support and engage the tube wallrepresents a very eifrcient measure preventing leakage of water or steamout into a draining channel 46, from which a draining pipe il conductssuitably to the collecting header I or into the conduit l.

As shown in Fig. 4 the upper headers are supported, substantially bymeans of ribs 36, by the 'the layer located inside saine.

smoke gas outlet made as a closed ring 3l. The ring 3l receives thecompressive stresses of the medium and transfers same to the shell,because it is in engagement with the bracket 38 which is fixedlyanchored in the shell, for instance by welding. The brackets 3Q and 33may, at the joining places be so shaped that they compel the two shellhalves to be maintained in their semicircuiar shape and they also serveas means, whereby the two halves remain anchored to one another, Fig. 4also shows, how the outlet 9 for superheated steam from header 20 may besuitably arranged.

'Ihe boiler tube shown in Fig. 5 may be for instance a vaporization andsuperheating tube I9 with an insertion member 39 which is shown indifferent shapes. 40a (Fig. 5a) represents means compelling the mediumto take a helical path forwards around the insertion member and 49h(Fig. 5) represent means acting as throttling members for thesuperheated steam.

As it is advantageous that the radiating heat as well as the highesttemperature of the smoke gases act only on the innermost layer of boilertubes I9, these tubes should be provided with s0- f called wings 48which may be welded to the tubes at their exterior side for instance asshown in Fig. 6. The wings t3 on adjacent tubes I9 may extendapproximately together (Fig. 6) to form members receiving the proportionof the radiati ing heat from wall I3 which radiates outwards betweentubes I9 and conducting the heat thus received inwards through thewelded joints to tubes and this will effect a good equalization of theheat tension which would otherwise rise on account of the heat radiationreceived by the tubes 9 direct from wall I3.

It is useful to arrange the different layers of boiler tubes I9 and I5in closed rings surrounding Each of their distributing and collectingheaders I'I, I8, I5, 20 are therefore also suitably shaped as a ringwhich, owing to the assembling of same with the shell 23, may be dividedup into two or more segments.

Such a ring-shaped collecting header 2|] may, as shown in Fig. 4, beheld in position inside a header I5 outside same, if desired with asmall recess therebetween to receive the asbestos cord 4I which preventsheat transmission from an inside hotter to an outside colder collectingheader r and may simultaneously form a tightening means which permitsthe expansion of the inner member. The outermost collecting ordistributing headers I5 and I'I are supported in the shell 23,

whereas the innermost one 20 carries the vault "1- I4 of the combustionchamber 2 (see Figs. l and 4), and the vault I4 also forms a stay forthe wall or layer 22 around the same.

Taken altogether, the different heat receiving members and other partsof the boiler may be shaped in a natural manner so that they tharmoniously together, so that they may be put or placed into eachother, support each other and maintain each other xedly and safely inposition within the closed boiler shell '23 enclosing the Whole. Theattaching together of the members by screws or bolts is avoided, and theboiler may be made with small dimensions as compared with its capacity.

By means of a construction according to the present invention the paths2, 3, 4 of the smoke gases may at all places be made with just the crosssection area required by the gases with regard to their temperature andto the velocity which may be safely imparted to them, and along bij thewhole path the gas enclosing walls may constitute eiicient heatingsurfaces.

Transverse obstructions and other things giving rise to unintentionaleddy formations are naturally avoided and on account of this fact inconnection with a somewhat greater drop in pressure which might beimparted to the smoke gases, the latter will attain a considerablyincreased velocity past the heating surfaces, so that not only theirarea may be reduced, but in addition the smoke gases will therebythemselves and owing to the narrow passages prevent ashes etc. takenalong with them from being deposited on the surfaces and from formingthe undesired heat-insulating coatings which usually must be Y removedby special means.

While a liquid medium is contained in the distributing header I8, fromwhich the vaporizing tubes I9 pass out, only a gaseous medium, accordingto the present invention, is present in the collecting header 29,wherein the tubes pass in. In other words there takes place in the tubesa total vaporization of liquid flowing in same. A further improvementconsists in this that the vaporization has been completed when themedium has passed only a portion of the tubes I9, Whereas the remainingportion of the tubes operates as a superheating tube. Consequently insuch case the steam will enter the -collecting header 20 in asuperheated state, whereby an extra superheater is avoided.

A technical progress also resides in the feature that in the passage ofthe boiler tubes I9 a bar 39, another tube or the like is placed. Thisinsertion member may suitably fill out the essential part of the saidpassage and is important in several respects. By means of this memberthe boiler tubes I9 may be made comparatively large, and still the gasquantity ilowing through same will not be too great in relation to theheating surface, even if no very high velocities of the mediumbe'chosen, and the insertion member 39, 49a may, similar to thewell-known twisted metal ribbons, impart to the medium a helical pathforwards, whereby well-known advantages are obtained.

A high increased velocity of the medium preferably several hundredmeters per second is of great importance in the construction hereindescribed, particularly if the medium is caused to vaporize completelywithin the tubes. As the velocity increases in direct proportion to theincrease in volume during the steam formation, an initial velocity whichis for instance doubled will correspond to a doubling of all velocitiesin front thereof. Consequently the heat transmission to the medium willincrease, and steam bubbles on the heating surfaces are easier sweptaway. It will suit the purpose to increase the pumping-work and to allowa comparatively great drop in pressure through the tubes. Thereby themedium in a very narrowed passage may be caused to take on such a highvelocity, especially in the superheating portion, that this wholeportion may really be considered as an elongated throttling devicecausing a rather eiiicient turbulating and obstructing influence(increasing with the square of the velocity) assisting in transmittingthe heat even to the superheated steam to such a degree that itapproaches the heat transmission to the medium in the ordinaryvaporization tubes. However, preferably the insertion member is madewith a shape as shown at 49D suitable to the purpose and causing anirregular eddy formation.

A helical'shape as shown at 40d and with a suitable pitch on thisportion will also cause an intensive eddy formation or a turbulatingaction throughout the medium, whereby the heat transmission will besufficient.

The comparatively great drop in pressure taking place through the tubeswill have the effect that the medium will be distributed practicallyuniformly in all tubes, even if the distributing and collecting headersare very narrow, and the medium therefore will flow in the tube passageswith a comparatively considerable velocity. These narrow and smallheaders represent great savings and a simplification of the Wholeconstruction.

'I'he insertion member may also be used to regulate the temperature ofthe tube proper in relation to the other tubes belonging to the samecollecting header on account of their own heat extension, wherebydetrimental heat stresses may be eliminated. The member 39 may expandfreely by heat and may, at a too high temperature in tube I9, cause adecrease in such temperature, and vice versa at .a too low temperaturein tube I9.

An embodiment of same is indicated in Fig. 8. As the pressure is higherin the distributing header I8 than in the collecting header 29, thetubes I9 are always pressed in the direction inwardly into header 20. Ifnow the insertion member 39 which is fixedly attached in header 2Uexpands by heat less than tube I9, its free lower end (Fig. 8) movesupwards relatively to the lower end of tube I9, thereby acting as acontrolling member for a narrowed passage porquantity passes to tube I9,whose temperature f will consequently increase.

The insertion member may also serve as a smoke gas tube. An examplethereof are the tubes 4 which constitute insertion members within thetubes I6 and which .are therefore swept by smoke gases.

As already mentioned it is advantageous, however, to arrange the lastand uttermost passages of the smoke gases in the boiler only in thesesmoke gas tubes 4, because thereby all the heat given off here will bereceived by the medium.

The member 39 may, if not removed in the manv ner explained below, betaken out after removal of the tightening plugs in the collectingheaders.

Thereby it is easy to clean the comparatively wide boiler tubes.

Further it is very important that the boiler tubes I6, I9 iilled withthe heat-receiving medium may slide with one or both ends in theirlongitudinal direction in the collecting or distributing header I8, 20,whereby any heat stress between the tubes owing to diiferentlongitudinal heat extension is totally avoided. The same appliesregarding the surrounding parts or the supporting places of thecollecting headers. It is particularly advantageous, if the tubes-as inthe construction indicated in the drawingsare not mere vaporizationtubes, wherein the temperature would be rather uniform for all tubes,but are combined water preheating or steamsuperheating tubes. The tubesmay suitably be attached in one header and be slidable in the other oneand they should be adapted to be quite withdrawn from the latter.Thereby the insertion member may be easily removed and the tubes beeasily cleaned, if necessary. If, as shown in the drawings, for theuttermo-st layer of boiler tubes IG, the insertion member is a smoke gastube 4, the inner tube (the insertion member 4 itself) and the outertube I6 may be attached each in its header I5 and I1 respectively,whereas they are slidable in the other header.

The tubes may be provided with tightening means, for instance asmentioned .above with a covered ring #l2 of copper or the like, wherethey pass out from their slide-support in the header. Owing to thedraining channels 46 the pressure is relieved from this tighteningmeans. These channels 6 may pass between the slide-supports all alongthe collecting header and in places where a preferably lower pressureprevails. The draining channel may be under atmospheric pressure, and inmany cases the leaked medium will be steam which is conducted into thefeed water.

The sleeves 45 are formed with a quite thin Wall, preferably of yellowmetal, thin enough to cause the over-pressure on one side to press itagainst the wall, if the sleeve is fixed to the tube, or against thetube, if it is fixed to the slide-support. In the most cases only onedraining channel is then necessary, at all events for the waterpreheating tubes. For the vaporization and superheater header one mayarrange a channel 41 conducting the leakage water from draining channel46 (Fig. 3) through the col lecting header I1 for the water preheatingtubes, and further through .a channel with a conduit out to the feedwater. Of course, these slidable tubes can not sustain the longitudinalcompressive stresses exerted by the medium. "Ihese stresses may becounter-acted by other members, however, for instance by the boilershell 23 proper, because the collecting and distributing headers mayeach be arranged in or be supported by brackets or supporting rings 3|,31 which in some way is in engagement with the boiler shell or isanchored thereto. Of course, the tubes I9 must be supported at certainplaces between the headers I8 and 29 against the occurring stressescaused by the breaking or end thrust forces.

The boiler as shown in the drawings is intended to be used for gaseousor liquid fuel producing a small radiation. The wall around thecombustion chamber will then serve as an indirect heating surface,because it receives heat from the gases by their sweeping over it and ittransmits it further by radiation to the boiler tubes arranged aroundsame. Such indirect heating surfaces might advantageously also bearranged in the interior of the combustion chamber, but in connectionwith coal powder stoking they will hardly be of ,any advantage seenapart from the fact that they would have a favorable influence upon thecombustion of the coal powder.

If the boiler is to be built for instance for coal powder, thecombustion chamber should have considerably greater dimensions, andwithin the wall should then also be mounted boiler tubes. The smokegases may then also during their return passage move along the exteriorside of the wall sweeping' the exterior side of the boiler tubesarranged around them, and may then pass through smoke gas tubes arrangedas insertion members in the interior of the boiler tubes.

When assembling, the beginning is made for instance with the one shellhalf. Then in proper order one half of the different members and partsis inserted, one inside the other one the insulating layer 2I, the waterpreheating members I5, I6, I1, insulating layer 22, vaporization andsuperheating members I8, I9, 20, ring 3I and intermediate superheater2B, 21a, 21h, 28, after having pushed in the wall I3 around thecombustion chamber and the supporting ring 32, 33 into its cavity. Thenthe vault and. the smoke gas outlet, the closed ring 31 are put inposition, whereupon follows the other half of the members mentionedabove but in the inverse succession.

When both boiler shells are anchored together, the interior members andparts are now also coupled together in their safe positions inside theboiler in a manner suitable with regard to heat extensions.

These different details represent separately, as also mentionedregarding some of them, more or less important technical progresses inthe steam boiler branch and assist in and form important links of theconstruction hereinafter described.

'Ihe invention comprises boilers for producing vapors from water andalso from other fluids.

I claim:

l. A water tube boiler comprising a central combustion chamber formedinside a combustion chamber wall, a plurality of layers of boiler tubessurrounding the said wall and spaced therefrom to provide between thewall and the innermost tube layer a smoke gas passage connected with theoutlet portion of the combustion chamber, collecting headers for theboiler tubes, the tubes of at least one tube layer being at an endmounted slidably in their headers, supports for the headers so arrangedat either end of the tubes as to prevent the headers from being pressedapart from one another longitudinally of the tubes, and an exteriorpulling member supporting in turn the said supports so as to receive astensile stresses the forces tending to press apart from one another theheaders at both ends of the boiler tubes.

2. A water tube boiler comprising a central combustion chamber formedinside a combustion chamber wall, a plurality of layers of boiler tubessurrounding the said wall and spaced therefrom to provide between thewall and the innermost tube layer a smoke gas passage connected with theoutlet portion of the combustion chamber, collecting headers for theboiler tubes, the tubes of at least one tube layer being at an endmounted slidably in their headers, supports for the headers so arrangedat either end of the tubes, as to prevent the headers from being pressedapart from one another longitudinally of the tubes, and an exteriorboiler shell supporting in turn the said supports so as to receive astensile stresses the forces tending to press apart from one another theheaders at both ends of the boiler tubes.

3. A water tube boiler comprising a central combustion chamber formedinside a combustion chamber wall, a plurality of layers of boiler tubesconnected in series and surrounding each other and the said wall andconducting water and steam in the longitudinal direction of the boiler,said tubes being spaced from the wall to provide between it and the tubelayers smoke gas passages connected with the outlet portion of thecombustion chamber to cause said gases to sweep the boiler tubes, meansto draw off the smoke gases after their having passed through saidpassages, collecting headers for the boiler tubes, the tubes of at leastone tube layer being at an end mounted slidablyin theirheaders,`supports for the headers so arranged at either end of the tubesas to prevent the headers from being pressed apart from one anotherlongitudinally of the tubes, and an exterior boiler shell supporting inturn the said supports so as to receive as tensile stresses the forcestending to press apart from one another the headers at both ends of theboiler tubes.

4. A water tube boiler according to claim 2, wherein the tubes of theinnermost layer are provided with wings welded thereto at the exteriortube side facing apart from the combustion chamber wall and so locatedas to receive not only heat from sweeping smoke gases but also theradiating heat passing from said wall outwards between the tubes andthereby to conduct such heat to the exterior sides of the tubes.

5. A water tube boiler according to claim 2, wherein the headers aremade annular and composed of segments.

6. A water tube boiler according to claim 2, wherein heat-insulatingmaterial is arranged between the two uttermost boiler tube layers, inorder to protect the surrounding boiler shell against heat.

'7. A water tube boiler according to claim l, providing in the interiorof the slidably mounted vaporizing boiler tubes members filling out anessential part of the tube passage area and obstructing thereby the flowof water and steam through the tubes so as to cause said tubes toVaporize the water received in one end from the collecting water headerand to superheat in the other tube end the steam produced in the middletube portion and to conduct such superheated steam to the header at saidother tube end, said members being combined with means acting toregulate by the heat expansion of the members the quantity of water andsteam passing through the tubes.

8. A water tube boiler according to claim 1, wherein the boiler tubesare so slidably mounted in their headers that they may be pulled quiteout from same longitudinally.

9. A water tube boiler according to claim 1, wherein the tubeslide-supports .of the headers are provided with at least one drainingchannel for leakage steam or leakage water, said channels being under alower pressure than that prevailing at the corresponding place in theinterior of the tubes.

10. A Water tube boiler according to claim 1, wherein the tubeslide-supports of the headers are provided with a tightening member inthe form of a sleeve formed with thin walls within the support.

11. A water tube boiler according to claim 1, wherein the tubeslide-supports of the headers are provided with a tightening member inthe form of a sleeve formed with thin walls within the support as anintegral portion of the tube end.

12. A water tube boiler according to claim 2, wherein the headers aremade in annular shape composed of segments contacting each other whenassembled and held together in position by the surrounding boiler shellWithout bolts or other connecting structure.

13. A water tube boiler according to claim 3, wherein between the heatradiating combustion wall and the boiler tube layer outside same meansare provided to receive a principal proportion of the heat transportedfrom the combustion chamber through said wall so as to protect to thegreatest possible extent the exterior boiler shell against heat.

14. A water tube boiler according to claim 3, wherein between the heatradiating combustion wall and the boiler tube layer loutside same anintermediate steam superheater is provided to receive a principalproportion of the heat transported from the combustion chamber throughsaid wall so as to protect to the greatest possible extent the exteriorboiler shell against heat.

JOHAN OLSEN NYGAARD.

